The invention relates to an ink jet recording head and a process of manufacturing such an ink jet recording head. More particularly, the invention is directed not only to an ink jet recording head with improved ink injecting speed at which ink is jetted out of the ink cavities, but also to a process of manufacturing such an ink jet recording head.
An ink jet recording head using a piezoelectric body element as an ink jetting drive source, i.e., as an element for converting electric energy to mechanical energy has heretofore been known. The piezoelectric body element is formed by interposing lead titanate zirconate (hereinafter referred to as "PZT") between a lower electrode and an upper electrode.
This ink jet recording head generally includes: a head substrate having a plurality of ink cavities formed therein; a vibrating plate mounted on the head substrate so as to cover all the ink cavities; a piezoelectric body element attached to portions of the vibrating plate corresponding to the ink cavities; and a nozzle plate arranged on the head substrate so as to close the ink cavities. It may be noted that the nozzle plate has ink jetting ports for jetting out ink contained within the ink cavities.
The thus constructed ink jet recording head is designed to displace the piezoelectric body element by applying an electric field thereto and to apply pressure to a desired ink cavity so that the ink contained in such a desired ink cavity is squeezed outward from a corresponding ink jetting port. Each of the cavities is formed to have such a capacity (volume) as to allow satisfactory printing to be carried out. Here, this ink jet recording head is designed to have as many ink cavities as possible in a narrow surface area so that reproducibility and artistic appearance of tiny characters, graphics, pictures, and the like can be improved. To achieve this object, the ink cavities are designed to be deep enough to reliably meet the aforementioned capacity (volume) requirement.
However, such a conventional ink jet recording head addresses the following problem. In the conventional ink jet recording head, the piezoelectric body element utilizing a thin-film piezoelectric mechanism is formed on the front surface of a silicon wafer and the ink cavities are laid out on the back surface of the silicon wafer at locations confronting the piezoelectric body element. Silicon wafers that can actually be handled during manufacturing processes are 100 mm in diameter and as thin as 200 .mu.m, and if ink cavities are formed at such a high density as to allow high-definition printing to be achieved, side walls partitioning individual ink cavities must be thin. As a result, the side walls are susceptible to deformation, which in turn prevents ink particles from being jetted therethrough efficiently as well as speedily.
Further, if an inexpensive silicon wafer that is 150 mm or more in diameter is used, the silicon wafer thickness that can be handled becomes about 500 .mu.m, which in turn requires that this wafer have deeper ink cavities. As a result, arises the problem that the side walls are susceptible to distortion and deformation due to displacement of the piezoelectric body element.
As a result, when pressure is applied to an ink cavity by displacement of the piezoelectric body element, it is difficult to utilize such pressure for correct and efficient ink jetting operation. Hence, the problem of impaired ink injecting speed occurs.